Ultrasonic flow meter systems are used for measuring the rate of fluid (e.g., gas or liquid) flow within a conduit such as a pipe. In one particular system, two transducers are disposed on the exterior of the conduit at an oblique angle to each other. One transducer is the upstream transducer and the other is the downstream transducer. The rate of fluid flow through the conduit is determined by first transmitting a pulse from the upstream transducer to the downstream transducer. Next, the downstream transducer transmits a pulse to the upstream transducer. The transit time of the pulse transmitted from the upstream transducer to the downstream transducer is less than the transit time of the pulse transmitted in the reverse direction and the fluid flow rate can be determined (calculated) based on the difference in the transit time of the two pulses. Those skilled in the art know that the transducers can be clamped on the exterior of the conduit or can be inserted through the wall of the conduit (e.g., “wetted transducers”).
A typical flow meter system includes the transducers and an electronic controller powered by a standard power supply. The controller controls the transducers and responds to the signals output by the transducers to calculate the flow rate. In some installations, for example when hazardous explosive gasses are present, the controller must be placed within an explosion proof enclosure. The power supply connections require cable conduits or other special handling typically required for wiring to an explosion proof enclosure. Presently available ultrasonic flow meters cannot be installed in their entirety, including the transducers and all of the flow meter electronics, in a hazardous area because they do not meet the specific requirements of hazardous areas as, for example, specified in EN50020 or Approval Standard Class Number 3610.
There are also uses for ultrasonic flow meters where a traditional power supply is not available. Presently designed flow meter controllers consume high power levels and presently available ultrasonic flow meter systems cannot generally be powered by alternative energy sources such as battery or solar power type supplies for an extended period of time.